In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA), sensors and/or User Equipment (UE), communicate via an access network such as a Radio Access Network (RAN) with one or more core networks (CN) or a Wi-Fi network. The RAN covers a geographical area which is divided into service areas or cell areas, which may also be referred to as a beam or a beam group, with each service area or cell area being served by a radio network node such as a radio access node e.g., a radio base station (RBS) or a Wi-Fi access point, which in some networks may also be denoted, for example, a NodeB, eNodeB (eNB), or Next Generation NodeB (gNB) as denoted in 5G. A service area or cell area is a geographical area where radio coverage is provided by the radio network node. The radio network node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio network node.
Specifications for the Evolved Packet System (EPS), also called a Fourth Generation (4G) network, have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases, for example to specify a Fifth Generation (5G) network also referred to as 5G New Radio (NR). The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access network wherein the radio network nodes are directly connected to the EPC core network rather than to RNCs used in 3G networks.
In general, LTE networks have support for a wide range of positioning methods. In order to fulfil high positioning accuracy requirements in different deployment conditions, the interest in hybrid solutions which explore two or more of these positioning methods at the same time are increasingly extended. Some sensor measurements in a target device, such as a UE, may provide useful information in terms of positioning in relation to a specific reference, such as e.g. a reference position and/or a reference time, such as e.g. a reference displacement time. In 3GPP Rel.14, support for barometric pressure sensor was introduced, thereby providing a solution for estimation of a vertical position of the UE. The ongoing 3GPP Rel.15 work item on accurate positioning includes support for sensor measurements.
A coordinate system in geography is a coordinate system that designates every location on earth with a specified set of numbers. This enables any location to have a specified vertical position and a horizontal position which allows a certain point to be located on the surface of the earth. A further set of numbers indicate the elevation of the same point with respect to a fixed datum, generally the sea level.
This can vary depending on the country or region under consideration. It is also possible to locate positions with Cartesian coordinates which gives the distances in all the three axes from a fixed point which is considered as the center of the earth, although it is the center of the mass of the earth which is actually considered, as this is easier to locate.
The absolute location helps to determine the location of a target device or a place with respect to certain coordinates that themselves have a fixed reference. A relative position or displacement of the target device is determined in reference to certain known locations or positions. The absolute location of the target device may be determined with the help of longitudinal and latitudinal lines. These indicate the position of the target device on the surface of the earth. The displacement from a known position to a position relative to the known position, i.e. the relative position, may herein also be referred to as a relative displacement. The term relative displacement and displacement may herein be used interchangeably.
The following positioning techniques are some of the techniques considered in LTE:
Assisted Global Navigation Satellite System (GNSS). GNSS information indicating an “absolute” position, e.g. in terms of coordinates, can sometimes be retrieved by the UE, supported by assistance information provided to the UE from E-SMLC.
Observed Time Difference of Arrival (OTDOA). The UE estimates the time difference of reference signals from different base stations and sends the resulting OTDOA to the E-SMLC for positioning of the UE by multi-lateration.
These position techniques are however battery consuming and have limitations when the UE is located indoors. In 3GPP Rel. 15 work item, solutions for improving indoor positioning have been discussed. These solutions suggest using sensors comprised in the UE to determine a displacement of the UE.
The varying UE capabilities in translating the sensor measurements to a displacement does however create an uncertainty at the location server regarding the quality of the displacement estimation.